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#include "keyword.h"void encode_keyword(char* plaintext, char* keyword){	int i ;	int j ;	int len = strlen(keyword) ;	int plen = strlen(plaintext) ;	// reduce the keyword to a number that can be easily	// added to the characters.	for(i = 0 ; i < len ; i++)	{		keyword[i] -= 'a' ;	}	for(i = 0 ; i < plen ; i+= len)	{		for(j = 0 ; j < len ; j++)		{			plaintext[i+j] = plaintext[i+j] + keyword[j] ;			while(plaintext[i+j] > 'z')			{				plaintext[i+j] -= 26 ;			}			if(i+j >= plen)			{				break ;			}		}	}	for(i = 0 ; i < len ; i++)	{		keyword[i] += 'a' ;	}		return ;}void decode_keyword(char* ciphertext, char* keyword){	int i ;	int j ;	int len = strlen(keyword) ;	int plen = strlen(ciphertext) ;	// reduce the keyword to a number that can be easily	// added to the characters.	for(i = 0 ; i < len ; i++)	{		keyword[i] -= 'a' ;	}	for(i = 0 ; i < plen ; i+= len)	{		for(j = 0 ; j < len ; j++)		{			ciphertext[i+j] = ciphertext[i+j] - keyword[j] ;			while(ciphertext[i+j] < 'a')			{				ciphertext[i+j] += 26 ;			}			if(i+j >= plen)			{				break ;			}		}	}	for(i = 0 ; i < len ; i++)	{		keyword[i] += 'a' ;	}		return ;}